Colorimetric chemical sensor with enhanced color sensitivity

ABSTRACT

A colorimetric sensor for detecting an analyte of interest in a fluid sample includes a lamellar photonic material having alternating layers of a first polymer layer and a second polymer layer. Each first polymer layer can be a molecularly imprinted polymer defining a cavity shaped to receive an analyte of interest. The photonic material is configured such that, when an analyte contacts the photonic material and becomes disposed within a cavity of the molecularly imprinted polymer, a refractive property of the photonic material changes, causing a detectable color change in the sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, claims priority to and thebenefit of, and incorporates by reference herein in its entiretyInternational Patent Application No. PCT/US2017/056553, which was filedon Oct. 13, 2017 and which claims priority to and the benefit of U.S.Provisional Patent Application No. 62/407,765, which was filed on Oct.13, 2016 and the content of which is also incorporated by referenceherein in its entirety.

TECHNICAL FIELD

In various embodiments, the present invention relates to a chemicalsensor for use in detecting the presence of a target analyte in a fluidsample and, more specifically, to a colorimetric chemical sensor havingalternating polymer layers for use in detecting a target analyte, forexample, a date rape drug, in a fluid sample.

BACKGROUND OF THE INVENTION

The use of agents to incapacitate an individual has become moreprevalent. Examples of such agents include gamma-butyrolactone (GBL),gamma-hydroxybutyrate (GHB), ketamine, Rohypnol, and the like. Forexample, the agents may be secretly placed in the beverage, such as analcoholic beverage, of the intended consumer. Because these and similaragents are colorless, substantially odorless, and hard to detect,methods and devices are needed to detect the presence of such agentsprior to consumption.

Although there are various techniques for detecting the presence of achemical substance in a subject after the subject has consumed such anagent (e.g., by urinalysis using liquid chromatography-tandem massspectrometry), such techniques are reactive in nature and merely confirmwhat may already be suspected, rather than proactive to detect the agentbefore it has been consumed. Furthermore, such techniques requireexpensive equipment run by highly trained technicians. Proactive testingdevices may require exposing a portion of the liquid to be tested to achemical reagent composition, which may result in a color change thatindicates the presence of the agent in the liquid sample. Unfortunately,such tests are time consuming and may not be discrete.

Additional testing apparatus are available. For example, a subject mayuse drug testing strips that are hidden in or incorporated into, forexample, a match, a match book, a cocktail napkin, a coaster, aplacemat, a menu, and so forth. Although such techniques may appear morediscreet, the subject may nevertheless be placed in an awkward positionby having to perform the test. Moreover, the subject may have to carryout tests periodically over the course of a social encounter.

U.S. Pat. No. 9,285,352 describes an apparatus for testing a liquidusing a straw, a stirrer, and/or a beverage container, where anindicator adapted to provide a visible reaction, e.g., a color change,upon exposure to an agent of interest may be adhered or otherwise bondedto a portion of the straw, stirrer, and/or beverage container. Inparticular, the indicator may cause the straw, stirrer, and/or beveragecontainer, or the liquid contacting the straw, stirrer, and/or beveragecontainer, to change color and/or fluoresce when an agent of interest isdetected at or above a certain concentration.

Despite the advances made to date, there still exists a need forimproved devices (e.g., colorimetric sensors) and methods for detectingchemical substances of interest in a liquid sample.

SUMMARY OF THE INVENTION

The invention is based, in part, upon the discovery of a newcolorimetric sensor that can detect an analyte of interest in a fluid orliquid sample and that, in some implementations, may be disposed upon orintegrated within a surface of a fluid receptacle (e.g., a glass or acup) or a straw.

In one aspect, the colorimetric sensor includes a lamellar photonicmaterial (e.g., a photonic gel or a photonic crystal) having alternatinglayers of a first polymer layer (e.g., a binding or receptor-containingpolymer) and a second polymer layer (e.g., polystyrene). Each firstpolymer layer may be a molecularly imprinted polymer defining a cavityshaped to receive an analyte of interest. The photonic material may beconfigured such that, when an analyte contacts the photonic material andbecomes disposed within a cavity of the molecularly imprinted polymer(i.e., the first polymer layer), a refractive property of the photonicmaterial changes, causing a detectable color change in the sensor. Thefirst polymer layer that is molecularly imprinted may contain achromophore-containing polymer such as poly(urea-naphthalimide),poly(thiourea-naphthalimide), poly(styrene-urea-naphthalimide) orpoly(styrene-thiourea-naphthalimide).

In certain applications, each first polymer layer is adapted such that,when the cavity receives the analyte of interest, the first polymerlayer changes volume relative to a second polymer layer, therebychanging the refractive property of the photonic material. In someimplementations, each first polymer layer further includes a chromophoreindicator (e.g., a naphthalimide moiety) such that, when the cavityreceives the analyte of interest, the analyte causes an electronicallyinduced color change of the chromophore indicator that amplifies thecolor change in the sensor. In some variations, the chromophoreindicator is incorporated into the first polymer layer as a co-polymer.

In certain embodiments, the alternating layers of the first and secondpolymer layers have a periodic distribution. In the absence of theanalyte of interest, the periodic distribution may be from about 1 nm toabout 1000 nm, or from about 100 nm to about 950 nm, or from about 200nm to about 900 nm, or from about 300 nm to about 850 nm, or from about400 nm to about 800 nm. In some embodiments, the periodic distributionin the presence of the analyte may be different from the periodicdistribution in the absence of the analyte.

In a second aspect, the invention provides a method for detecting ananalyte of interest in a fluid sample, which includes contacting acolorimetric sensor of the invention with a fluid sample to beinterrogated and detecting whether a color change occurs when the sensoris contacted with the fluid sample. A color change being indicative thatthe analyte is present in the fluid sample. In certain embodiments, thecolorimetric sensor includes a lamellar photonic material (e.g., aphotonic gel or a photonic crystal) having alternating layers of a firstpolymer layer and a second polymer layer as described herein.Advantageously, in some implementations, the photonic material isconfigured so that, when an analyte contacts the photonic material andbecomes disposed within a cavity of the molecularly imprinted polymer, arefractive property of the photonic material changes, causing adetectable color change in the sensor.

In certain embodiments, each first polymer layer is adapted such that,when the cavity receives the analyte of interest, the first polymerlayer changes volume relative to a second polymer layer, therebychanging the refractive property of the photonic material. In certainembodiments, each first polymer layer further includes a chromophoreindicator (e.g., a naphthalimide-containing moiety) such that, when thecavity receives the analyte of interest, the analyte causes anelectronically induced color change of the chromophore indicator thatamplifies the color change in the sensor. In some variations, thechromophore indicator is incorporated into the first polymer layer as aco-polymer.

In certain embodiments, the alternating layers of the first and secondpolymer layers have a periodic distribution. In the absence of theanalyte of interest, the periodic distribution may be from about 1 nm toabout 1000 nm, or from about 100 nm to about 950 nm, or from about 200nm to about 900 nm, or from about 300 nm to about 850 nm, or from about400 nm to about 800 nm. In some implementations, the periodicdistribution in the presence of the analyte may be different from theperiodic distribution in the absence of the analyte.

In another aspect, the invention provides a method of manufacturing acolorimetric sensor capable of detecting an analyte of interest in afluid sample. In some embodiments, the method includes creating a firstset of spaced apart layers of a first polymer. Each layer of the firstset of spaced apart layers of the first polymer can be a molecularlyimprinted polymer that defines a cavity shaped to receive an analyte ofinterest. The method may also include imprinting (e.g., using a stampand/or a mold) the first set of layers into a coating that is orincludes a second polymer (e.g., polystyrene), thereby creating aphotonic material having alternating layers of first and second polymersconfigured such that, when an analyte contacts the photonic material andbecomes disposed within a cavity of the molecularly imprinted polymer, arefractive property of the photonic material changes thereby to cause adetectable color change in the sensor.

In certain embodiments, the coating that is or includes the secondpolymer is disposed upon the surface of a substrate, e.g., a fluidreceptacle (e.g., a cup, a glass, or the like) or a straw. In certainembodiments, the first set of spaced apart layers is disposed upon arelease medium with anti-adhesive properties, e.g., a hydrophobicmonolayer molecular coating such as a fluorinated self-assembledmonolayer, a fluorinated diamond-like carbon coating, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. For the purposes of clarity, notevery component may be labeled in every drawing. Also, the drawings arenot necessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIG. 1A schematically illustrates a colorimetric sensor reflecting afirst color (e.g., blue) due to an initial local refractive index of afirst polymer material in accordance with embodiments of the invention;

FIG. 1B schematically illustrates a colorimetric sensor reflecting asecond, different color (e.g., red) due to a change in the localrefractive index of the first polymer material of FIG. 1A caused bybinding the analyte of interest;

FIG. 1C schematically illustrates a photonic crystal which can act as acolorimetric sensor in accordance with embodiments of the invention;

FIG. 1D schematically illustrates a photonic crystal which can act as acolorimetric sensor in accordance with embodiments of the invention;

FIG. 2 schematically illustrates a molecularly imprinted polymer (MIP;225) in a first polymer layer of a colorimetric sensor capturing targetanalyte molecules (300) in accordance with embodiments of the invention;

FIGS. 3A and 3B schematically illustrate a first bottom-up method ofmanufacturing a colorimetric sensor for detecting an analyte of interestin a fluid sample in accordance with embodiments of the invention;

FIG. 4 schematically illustrates second bottom-up method ofmanufacturing a colorimetric sensor for detecting an analyte of interestin a fluid sample in accordance with embodiments of the invention;

FIGS. 5A-5D schematically illustrate a top-down method of manufacturinga colorimetric sensor for detecting an analyte of interest in a fluidsample in accordance with embodiments of the invention; and

FIG. 6 schematically illustrates exemplary substrates for use incombination with colorimetric sensors for detecting an analyte ofinterest in a fluid sample in accordance with various embodiments of theinvention.

DETAILED DESCRIPTION

To provide an overall understanding of the invention, certainillustrative embodiments will now be described, including devices (e.g.,colorimetric sensors), methods of making the devices, and methods ofdetecting an analyte of interest in a fluid sample. However, the devicesand methods described herein may be adapted and modified as appropriatefor the application being addressed and that the devices and methodsdescribed herein may be employed in other suitable applications. Allsuch adaptations and modifications are to be considered within the scopeof the invention.

Throughout the description, where compositions and devices such as asensor are described as having, including, or comprising specificcomponents, or where processes and methods are described as having,including, or comprising specific steps, it is contemplated that,additionally, there are compositions and devices of the presentdisclosure that consist essentially of, or consist of, the recitedcomponents, and that there are processes and methods according to thepresent disclosure that consist essentially of, or consist of, therecited processing steps.

In the application, where an element or component is said to be includedin and/or selected from a list of recited elements or components, itshould be understood that the element or component can be any one of therecited elements or components, or the element or component can beselected from a group consisting of two or more of the recited elementsor components.

Further, it should be understood that elements and/or features of adevice or a method described herein can be combined in a variety of wayswithout departing from the spirit and scope of the present disclosure,whether explicit or implicit herein. For example, where reference ismade to a particular feature, that feature can be used in variousembodiments of devices of the present disclosure and/or in methods ofthe present disclosure, unless otherwise understood from the context. Inother words, within this application, embodiments have been describedand depicted in a way that enables a clear and concise application to bewritten and drawn, but it is intended and will be appreciated thatembodiments can be variously combined or separated without parting fromthe present teachings and disclosure(s). For example, it will beappreciated that all features described and depicted herein can beapplicable to all aspects of the disclosure(s) described and depictedherein.

The articles “a” and “an” are used in this disclosure to refer to one ormore than one (i.e., to at least one) of the grammatical object of thearticle, unless the context is inappropriate. By way of example, “anelement” means one element or more than one element.

The term “and/or” is used in this disclosure to mean either “and” or“or” unless indicated otherwise.

It should be understood that the expression “at least one of” includesindividually each of the recited objects after the expression and thevarious combinations of two or more of the recited objects unlessotherwise understood from the context and use. The expression “and/or”in connection with three or more recited objects should be understood tohave the same meaning unless otherwise understood from the context.

The use of the term “include,” “includes,” “including,” “have,” “has,”“having,” “contain,” “contains,” or “containing,” including grammaticalequivalents thereof, should be understood generally as open-ended andnon-limiting, for example, not excluding additional unrecited elementsor steps, unless otherwise specifically stated or understood from thecontext.

Where the use of the term “about” is before a quantitative value, thepresent disclosure also includes the specific quantitative value itself,unless specifically stated otherwise. As used herein, the term “about”refers to a ±10% variation from the nominal value unless otherwiseindicated or inferred.

Where a percentage is provided with respect to an amount of a componentor material in a composition such as a polymer, the percentage should beunderstood to be a percentage based on weight, unless otherwise statedor understood from the context.

Where a molecular weight is provided and not an absolute value, forexample, of a polymer, then the molecular weight should be understood tobe an average molecule weight, unless otherwise stated or understoodfrom the context.

It should be understood that the order of steps or order for performingcertain actions is immaterial so long as the present disclosure remainsoperable. Moreover, two or more steps or actions can be conductedsimultaneously.

At various places in the present specification, features are disclosedin groups or in ranges. It is specifically intended that the descriptioninclude each and every individual subcombination of the members of suchgroups and ranges. For example, an integer in the range of 0 to 40 isspecifically intended to individually disclose 0, 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40, and aninteger in the range of 1 to 20 is specifically intended to individuallydisclose 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, and 20.

The use of any and all examples, or exemplary language herein, forexample, “such as” or “including,” is intended merely to illustratebetter the present disclosure and does not pose a limitation on thescope of the disclosure unless claimed. No language in the specificationshould be construed as indicating any non-claimed element as essentialto the practice of the present disclosure.

Various aspects of the disclosure are set forth herein under headingsand/or in sections for clarity; however, it is understood that allaspects, embodiments, or features of the disclosure described in oneparticular section are not to be limited to that particular section butrather can apply to any aspect, embodiment, or feature of the presentdisclosure.

In some implementations, the present invention involves a specificbinding event(s) that, advantageously, may result in a change in thecomposition and/or the shape of a dielectric arrangement of lamellarphotonic material. Such change(s) may induce at least two exemplaryobservable colorimetric effects. First, a reflecting color change mayoccur due to a local refractive index change, for example, due to thepresence of an analyte in a cavity of a first polymer (e.g., an MIP)and/or due to swelling of a first polymer layer due to the presence ofthe analyte in a cavity. More particularly, reflectivity may beselectively tuned to a desired wavelength(s) (e.g., within the visiblespectrum and/or near infrared) by selectively modulating the opticalthickness of a discrete layer of a polymeric phase due to swellingcaused by binding of one or more specific analyte target molecules tothe polymeric phase, which may change the photonic band gap and thereflected color. Second, a coordination complex of a specific analytetarget molecule with a chromophore indicator (for example, incorporatedinto a polymer) may also result in a color change due to, for example,the intrinsic change of electronic state. Consequently, in someimplementations, due to the second effect, the color change may be“amplified” so that an enhanced color contrast is seen upon the bindingof one or more specific analyte target molecules to the chromophore ofthe polymeric phase. In some implementations, the color contrast may beincreased or decreased as desired by tuning the interplay of the twocolorimetric sensing mechanisms.

Device with Selectively Tunable Reflectivity

In certain embodiments, a colorimetric sensor of the invention isemployed to detect an analyte of interest in a fluid sample. The sensormay include a lamellar photonic material having alternating layers of afirst polymer layer and a second polymer layer. Each first polymer layermay be a molecularly imprinted polymer that defines a cavity shaped toreceive an analyte of interest. The photonic material may be configuredsuch that, when an analyte contacts the photonic material and becomesdisposed within a cavity of the molecularly imprinted polymer, arefractive property of the photonic material changes, causing adetectable color change in the sensor. In various embodiments, thesensor (see, e.g., FIGS. 1A-1C) functions in a similar fashion to aBragg reflector (or “Bragg mirror”). In other embodiments, the sensor(see, e.g., FIG. 1D) functions in a similar fashion to a diffractiongrating.

Bragg diffraction, which results from the constructive interference ofreflected light, occurs when reflected light passing through multiplelayers of alternating materials remains in phase owing to the periodicdistribution or periodicity of the spacing between the layering. Forexample, if the periodic distribution of the alternating layers ismaintained at an integer multiple of the desired reflected wavelength(k), then a device with a band gap that selectively reflects light of aparticular wavelength can be formed. For example, within the visiblespectrum, blue light has a wavelength of about 450-495 nm, and red lighthas a wavelength of about 620-750 nm. Thus, a device with a periodicdistribution of about 450-495 nm reflects blue light, whereas a devicewith a periodic distribution of about 620-750 nm reflects red light.

As is known in the art, the periodic modulation of differing dielectricproperties (e.g., refractive indices) between plural (e.g., two)alternating layers of materials may also be used to create photoniccrystals to form a band gap to selectively reflect light of a particularwavelength. Periodic modulation may occur in one-dimensional (e.g.,lamellar) structures, two-dimensional structures, or three-dimensionalstructures. For example, a lamellar distributed Bragg reflector (orBragg mirror) may include a stack of film layers having alternating highrefractive index (n₁) and low refractive index (n₂) materials, in whicheach film layer may have a thickness of a quarter wavelength (λ/4). Aslight passes from a lower refractive index layer into a higherrefractive index material, the light reflected at the surface of thehigher refractive index material undergoes a 180-degree phase shift;however, as light passes from a higher refractive index layer into alower refractive index material, the reflected light at the surface ofthe lower refractive index material interferes constructively,increasing the intensity of the reflected light.

An illustrative embodiment of a colorimetric chemical sensor withenhanced color sensitivity, which functions in a similar fashion to aBragg reflector or Bragg mirror, is shown in FIGS. 1A and 1B.Advantageously, a sensor may be optically tuned to a selected wavelength(e.g., 450-495 nm) associated with a desired visible color (e.g., bluelight) as a function of the reflectivity (or periodicity) of thelamellar photonic material making up the sensor and, more specifically,may enable users to selectively modulate the optical thickness ofdiscrete sensor layers, e.g., via swelling (e.g., to about 620-750 nm)due to adherence or adsorption of an analyte target molecule(s) to thesensor. The adherence or adsorption and/or a swelling effect can changethe photonic bandgap as well as the reflected color (e.g., to red light)that may be seen by the user.

FIG. 1A shows, for example, a sensor 100 in an original state that, dueto the thicknesses of the first polymer layer 101 and the second polymerlayer 102 and/or the refractive indices (n₁, n₂) of each of the polymerlayers 101, 102, may appear as a first color at a shorter wavelength ofthe visible spectrum (e.g., blue). As shown in FIG. 1B, a volume and/orlayer thickness change in the first polymer layer 101′ due to swellingmay modify the photonic band gap and the reflecting color of thematerial, which provides indicia of the presence of the analyte targetmolecule(s). In some implementations, the change in refractive index,for example, due to swelling, may appear or manifest as an optimizedcolor toward the longer wavelengths of the visible spectrum (e.g., red).

In some variations, the sensors of the invention are one-dimensionalphotonic crystals. In general, there are two kinds of one-dimensionalphotonic crystal structures, each of which features a lamellar photonicmaterial having alternating layers 101, 102 of (e.g., two or more)discrete polymeric phases. In a first embodiment depicted in FIG. 1C,the alternating layers 101, 102 are stacked on top of each other alongthe z-axis and upon a substrate 103, such that only a single bottomlayer 102 makes direct contact with substrate 103. In this embodiment,the sensor 100 functions in a manner similar to a Bragg reflector orBragg mirror, as described above. In contrast, in a second embodimentdepicted in FIG. 1D, the alternating layers 101, 102 are disposed nextto each other along the x-axis and upon the substrate 103, such thateach alternating layer 101, 102 makes direct contact with substrate 103.In this embodiment, the sensor 100 functions in a similar fashion to adiffraction grating. As described further below, the substrate 103 canbe adhered, or otherwise attached to, a surface of interest, forexample, the surface of a cup or a straw.

In the embodiment depicted in FIG. 1D, sensor 100 includes a series ofrepeating layers 101, 102 that vary periodically in one dimension withtwo different refractive indices (n₁, n₂). In general, light incident onthe grating surface is scattered into several “orders” of bothtransmitted and reflected waves. The diffraction orders exist at varyingangles to the grating surface and are numbered such that the order whichis equivalent to the reflected and transmitted wave from a smoothsurface is the 0^(th) order, each subsequent order of a smaller orlarger angle is given −1 and +1 numbers, respectively, and the order ofeach successive angle decrease or increase is respectively decremented(e.g., −2, −3, etc.) or incremented (e.g., +2, +3, etc.) appropriately.

Initially, in the absence of analyte target molecule(s) and at a givenangle of observation, the diffraction grating reflects a selectedwavelength (e.g., 450-495 nm) associated with a first visible color(e.g., blue light). When, however, the physical geometry of thediffraction grating is manipulated, e.g., via swelling of the polymerlayer 101 in a vertical direction along the z-axis due to the adherence,binding or absorption of an analyte target molecule(s), the diffractiongrating will, at the same given angle of observation, reflect a second,different wavelength (e.g., 620-750 nm) of the incident light, whichleads to an observable color change in the sensor 100 (e.g., from blueto red).

The color reflected by a diffraction grating also depends, however, onthe angle at which a user observes the diffraction grating. Because ofthis, sensor 100 depicted in FIG. 1D is, in one embodiment, employed inconnection with a reference. The reference (not shown) may be the sameas (e.g., identical to) the depicted sensor 100 and may be placed on thesame plane as the depicted sensor 100 so that, in operation, the angleof observation is the same for both the depicted sensor 100 and thereference. The reference, however, may be covered with a transparentmaterial, such as a plastic or glass, that is impervious to, and thusprevents the introduction of analyte into the reference. In this way,both the depicted sensor 100 and the reference reflect, in the absenceof analyte, the same wavelength of the incident light and appear to bethe same color, regardless of the angle at which a user observes thedepicted sensor 100 and its reference. In the presence of analyte,however, the depicted sensor 100 and the reference appear as differentcolors, as the analytes will only have been adhered to, bound orabsorbed by the depicted sensor 100.

In one embodiment, the sensors described herein are thin films. Forexample, in the embodiments depicted in FIGS. 1C and 1D, the thicknessof the thin film along the z-axis may be on the micron scale (e.g.,about 1 μm to about 1000 μm, about 10 μm to about 1000 μm, about 100 μmto about 1000 μm, about 1 μm to about 100 μm, about 1 μm to about 10μm), while the lateral dimensions of the thin film along the x- andy-axes may on the centimeter scale (e.g., about 1 cm to about 1000 cm,about 10 cm to about 1000 cm, about 100 cm to about 1000 cm, about 1 cmto about 100 cm, about 1 cm to about 10 cm).

For the purpose of illustration and not limitation, illustrativeembodiments of the invention are described for a sensor that functionsin a similar fashion to a Bragg reflector or Bragg mirror and that, upondetecting an analyte of interest, transitions from reflecting aninitial, blue light (λ=450-495 nm) to reflecting a red light (λ=620-750nm) to provide an indication of the presence of the analyte of interestdetectable by the unaided eye. Those of ordinary skill in the art canappreciate that sensors of the invention may use transitions from anyspectral color having a first wavelength to another spectral colorhaving a second, different wavelength.

Preferably, the first polymer layer and second polymer layer have aperiodic distribution within the device such that, in a first state(i.e., as illustrated in FIG. 1A), a distance or height from the top ofone first polymer layer to the top of any other first polymer layer isan integer multiple of the wavelength of the desired reflected color(e.g., 450p to 495p nm, where p is an integer). For example, the desiredwavelength can be selected from wavelengths between about 1 nm to about1000 nm, between about 100 nm to about 950 nm, between about 200 nm toabout 900 nm, between about 300 nm to about 850 nm, and between about400 nm to about 800 nm, which latter range covers the visible lightspectrum. For exemplary embodiments using an initial, blue light, aperiodic distribution between about 450 nm and about 495 nm may beappropriate.

In various embodiments, the first polymer layer is a hydrophilicpolymer. A block co-polymer of a first polymer layer that is hydrophilicand a second polymer layer that is hydrophobic permits the first polymerdomains and the second polymer domains to self-assemble into a structure(photonic material or sensor) having alternating first and secondpolymer layers as described herein.

The first polymer layer can include a chemical moiety (e.g., a“receptor” or “binding site”) that can form a complex (e.g., host-guestchemistry) with an analyte target molecule of interest via anon-covalent bond, for example, via hydrogen bonding, metalcoordination, hydrophobic forces, van der Waals forces, π-πinteractions, halogen bonding, and/or electrostatic and/orelectromagnetic effects. The use of such a receptor can facilitatepositioning of the analyte during creation a molecularly imprinted firstpolymer layer. Such a receptor can facilitate an analyte positioningitself in a cavity of the molecularly imprinted first polymer layerduring use. Examples of such chemical moieties (receptors) include urea,thiourea, guanidine, aminopyridine, or amidine, cucurbituril,cyclodextrin, calixarene, crown ether, porphyrin, phthalocyanine, andthe like. See, e.g., “Current developments in fluorescent PET(photoinduced electron transfer) sensors and switches,” CHEM. SOC. REV.(2015), 44: 4203-4211; and Jonathan W. Steed, Jerry L. Atwood, Philip A.Gale, “Definition and Emergence of Supramolecular Chemistry,” chapter inSUPRAMOLECULAR CHEMISTRY: FROM MOLECULES TO NANOMAIERIALS (2012).

In various embodiments, for the purpose of selectively binding ordisposing one or more analyte target molecules to or in the firstpolymer layer, the first polymer layer can include or can be amolecularly imprinted polymer (MIP) characterized by one or morecavities formed in the matrix of the first polymer layer, where thecavities have an affinity (e.g., physical and/or chemical) for ananalyte of interest. MIPs are described in U.S. Pat. Nos. 8,241,575 and9,285,352, the contents of which are incorporated by reference herein intheir entirety for all purposes.

For example, a first polymer layer that is or includes a MIP may beformed by any molecular imprinting technique (e.g., a reversibleaddition-fragmentation chain transfer (RAFT) polymerization method, anatom-transfer radical polymerization (ATRP) method, a covalent bondingmethod, a self-assembly method, a hierarchical imprinting method, apolymerization packed bed method, or the like) that can leave a cavityin the first polymer layer, which cavity has an affinity to a chosen“analyte” molecule. In certain approaches, the process may involveinitiating the polymerization of monomers in the presence of an analyteof interest that is then extracted leaving behind a cavity that iscomplementary in three-dimensional shape to, or a mirror image of, thethree-dimensional surface of at least a portion of the analyte.

For example, the first polymer layer can include a monomer and acrosslinker, for example, a polymerizable monomer optionally with areceptor that can bind with an analyte molecule, such as urea orthiourea receptors, and a cross-linkable monomer that contains two ormore reactive groups such a one vinyl moiety and one allylic moiety.Each of the two or more reactive groups should have differentreactivities such that they can be employed in different stages of themanufacture of the first polymer layer. For example, a vinyl group canbe employed for incorporation into a pre-polymer for the first polymerlayer while the less reactive allylic functional group can be used as acrosslinker during the molecularly imprinting process. Otherasymmetrically divinyl or vinyl/allyl or other monomer with two doublebonds of different reactivity can be used, for example,methacrylate-based divinyl monomers such as hex-5-enyl methacrylate.See, e.g., “Controlled Divinyl Monomer Polymerization Mediated by LewisPairs: A Powerful Synthetic Strategy for Functional Polymers,” ACS MACROLETT. (2014), 3: 896-899 and “Branched polystyrene with abundant pendantvinyl functional groups from asymmetric divinyl monomer”, JOURNAL OFPOLYMER SCIENCE: PART A: POLYMER CHEMISTRY (2008), 46: 6023-6034.

The first polymer layer optionally can also include a chromophore. Thechromophores include molecules that can form a complex with an analyteto induce a photo-induced electron transfer. For example, the firstpolymer layer can include a naphthalimide-containing molecularlyimprinted polymer, for example, naphthalimide-based chromogenicmolecules and/or their derivatives such as a1,8-naphthalimide-containing polymer having a urea or thiourea moietypresent (e.g., poly(urea-naphthalimide) orpoly(thiourea-naphthalimide)). A chromophore can be used to enhance thecolor appearance and contrast. When a carboxylate ion is present, itforms a complex with urea or thiourea. The complex formation can changethe electron density of the naphthalimide moiety leading to an opticalabsorption change. A suitable Bragg resonance can enhance such anoptical change with a better saturation of the hue. For example, thecolor may be enhanced from a dull red to a very bright red so that ahuman observer can easily identify a color change, especially underdiffuse illumination or low light conditions.

In various embodiments, a naphthalimide-based fluorescence indicatormonomer can be integrated into the first polymer layer. The monomer cancontain a urea binding site to respond to carboxylate-containinganalytes that result in absorption and fluorescence change. Specificsubstitutions on the naphthalimide core may provide a binding partnerfor a carboxylate group present on an analyte of interest such as NaGHB.Furthermore, the naphthalimide can be functionalized with an alkenegroup so that it can be incorporated into a MIP. The binding of analytecan change the electron density in the naphthalimide aromatic ring andcause a change in the optical absorption properties. By combining theoptical absorber (such as but not limiting to a chromophore) withstructural color, the saturation of the color can be tuned so that it ismore easily distinguished by the unaided eye.

Examples of chromophores can include xanthene derivatives: fluorescein,rhodamine, Oregon green, eosin, and Texas red; cyanine derivatives:cyanine, indocarbocyanine, oxacarbocyanine, thiacarbocyanine, andmerocyanine; squaraine derivatives and ring-substituted squaraines,including Seta, SeTau, and Square dyes; naphthalene derivatives(including dansyl and prodan derivatives); coumarin derivatives;oxadiazole derivatives: pyridyloxazole, nitrobenzoxadiazole andbenzoxadiazole; anthracene derivatives: anthraquinones, including DRAQ5,DRAQ7 and CyTRAK Orange; pyrene derivatives: cascade blue and the like;oxazine derivatives: Nile red, Nile blue, cresyl violet, and oxazine170; acridine derivatives: proflavin, acridine orange, and acridineyellow; arylmethine derivatives: auramine, crystal violet, malachitegreen; tetrapyrrole derivatives: porphyrin, phthalocyanine, andbilirubin; and BODIPY dyes. See, e.g., “Current developments influorescent PET (photoinduced electron transfer) sensors and switches,”CHEM. SOC. REV. (2015), 44: 4203-4211; “Fluorescent PET (PhotoinducedElectron Transfer) sensors as potent analytical tools,” ANALYST (2009),134: 2385-2393; “Colorimetric “Naked Eye” Sensing of Anions in AqueousSolution,” J. ORG. CHEM. (2005), 70: 10875-10878, “Why, on Interactionof Urea-Based Receptors with Fluoride, Beautiful Colors Develop,” J.ORG. CHEM. (2005), 70: 5717-5720; and “Colorimetric and fluorescentanion sensors: an overview of recent developments in the use of1,8-naphthalimide-based chemosensors,” CHEM. SOC. REV. (2010), 39:3936-3953.

In certain embodiments, a first polymer layer can be formed from across-linkable monomer and a polymerizable monomer containing apolymerizable moiety, a receptor and a chromophore (e.g.,poly(styrene-urea-naphthalimide)) as depicted in Scheme I below.

The result of RAFT polymerization of the reactants in Scheme I, i.e.,the cross-linkable monomer and the polymerizable monomer, is a“pre-polymer” that includes a terminal RAFT agent. The pre-polymertypically is a soluble pre-polymer, which facilitates further creationof the first polymer layer.

Subsequently, as shown in Scheme II below, the pre-polymer can becombined with an analyte of interest (“analyte template”) to perform themolecularly imprinting process thereby creating the cavities for theanalyte. More specifically, the pre-polymer and analyte interact toassociate the analytes with the urea receptors, which pre-polymer can becrosslinked to form the cavities after the analyte is removed from theMIP (e.g., by Soxlet extraction and/or solvent washing processes). Ascan be seen across the first row of Scheme II, the first polymer layer(MIP) is formed, which can include a RAFT agent at its terminal end.Advantageously, the functional groups of the RAFT agent, including athiol group after reduction of the RAFT agent, can be used to secure thefirst polymer layer to a substrate such as in the top-down method ofmanufacturing discussed herein. The MIP at the end of this process alsocan be used to create a photonic material or sensor of the invention ina bottom-up layer-by-layer approach.

Scheme II also includes in its second row the formation of a blockco-polymer of the MIP with polystyrene by polymerization, for example,by RAFT polymerization, with styrene. Such a block co-polymer then canself-assemble into the alternating layers first and second polymerlayers of the photonic material or sensor.

Alternatively, as shown in Scheme III below, the pre-polymer is reactedwith styrene (which creates the second polymer layer) via RAFTpolymerization to form a block co-polymer of the first polymer layerwith the second polymer layer. The product of this reaction can be mixedwith an analyte of interest to create a molecularly imprinted polymer(MIP) resulting in the block co-polymer of the MIP (first polymer layer)and hydrophobic second polymer layer that can be self-assembled intoalternating layers of the first and second polymer layers.

With respect to the formation of the self-assembled structure ofalternating first and second polymer layers, the block co-polymer can bedissolved in appropriate solvent (e.g., propylene glycol monomethylether acetate (5 wt %)) to make homogeneous solution. Then a smallamount of co-polymer solution can be spin-cast onto a suitable substratesuch as glass or glass-like substrates. The glass can have a surfacetreatment appropriate for the intended use, for example, a surfacetreated either with (3-aminopropyl)triethoxysilane or with(3-iodopropyl)trimethoxysilane, or a surface treated with a thinmetallic film coating. The thickness of the metal film can be in therange of about 1 μm to about 1000 μm. One-dimensional lamellarstructures can be formed via thermal annealing at low temperature (suchas 50° C. for 24 hours) in a suitable vapor such as chloroform. See,e.g., “Broad-wavelength-range chemically tunable block-copolymerphotonic gels,” NATURE MATER. (2007), 6: 957-960.

Those of ordinary skill in the art can appreciate that each firstpolymer layer in a sensor of the invention may include any number ofcavities appropriate to achieve the intended purpose. The number ofcavities in a first polymer layer is, in part, determined by thedissociation constant of the material used for the first polymer layer.As different materials will have different dissociation constants, thenumber of cavities present in a first polymer layer will depend upon thetype of material employed as the first polymer layer. In general,however, the average density of the cavities in a first polymer layerwill be very high (e.g., up to 10¹⁰, 10¹⁵ or 10²⁰ cavities per gram offirst polymer). There may also be some variation in the number, density,and arrangement (e.g., distribution or pattern) of the cavities in thevarious first polymer layers, so long as each first polymer layercaptures substantially the same number of analytes of interest andswells by substantially the same amount so as to create a color contrastwith the sensor's original state in the absence of the analytes ofinterest.

Each formed cavity in the first polymer layer should have an affinityfor a corresponding analyte of interest, which may include, for thepurpose of illustration and not limitation, GBL, GHB, ketamine,Rohypnol, other pharmaceutical grade drugs, bacteria, allergens andproteins, 3-methyl-2-butene-1-thiol, substances that may be createdduring a process of creating 3-methyl-2-butene-1-thiol, substances thatmay be created when beer is exposed to sunlight, congeners (e.g.,produced during fermentation and/or distillation of a beverage), and soforth.

In some embodiments, the second polymer layer is a hydrophobic polymer.A block co-polymer of a second polymer layer that is hydrophobic and afirst polymer layer that is hydrophilic permits the first polymerdomains and the second polymer domains to self-assemble into a structure(photonic material or sensor) having alternating first and secondpolymer layers as described herein.

The second polymer layer may be a polymer of the type that may beincorporated into, e.g., plastic cups, bottles (or otherfood/beverage/liquid containers), stirrers, straws, utensils, gloves,contraception devices, feminine hygiene products, and so forth. Forexample, materials for the second polymer layer may include polystyrene,substituted polystyrene, modified polystyrene, polyethylene,polypropylene, poly(vinyl chloride), and poly(vinylpyridine). A desiredcharacteristic of material for a second polymer layer is that it doesnot change volume (e.g., swell) in the presence of the analyte ofinterest and/or the solvent/beverage being tested, or does not changevolume in the presence of the analyte and/or the solvent/beverage beingtested as much as the first polymer layer.

The second polymer layer may have a certain porosity that allows liquidto permeate through it to permit access to the internally-locatedsurfaces including cavities and receptors, if present, of the firstpolymer layers in a self-assembled structure. The thickness of a thinfilm of such a structure is on the order of microns, such that a liquidshould be able to diffuse through the alternating first and secondpolymer layers and/or to move via capillary action into the internalarea of the alternating layers of the sensor.

In various embodiments of the invention, the affinity of a cavity forits corresponding analyte of interest causes a selective volume changein the first polymer layer when the analyte of interest adheres to,binds or is adsorbed or is disposed in a cavity of the MIP. For example,in the sensors depicted in FIGS. 1A-1C, the volume change typicallyresults in a corresponding increase in height in the first polymer layerand in the periodic distribution between first and second polymerlayers, which results in a visible change in color. For example, if thesensor initially has a periodic distribution of about 450-495 nm toreflect blue light, but a volume change causes the periodic distributionto be about 620-750 nm, then red light would be reflected and visibleinstead of blue light. Volume and height increases can be referred to asthe “swelling” of the first polymer layer. In the self-assembly process,the amount of volume and/or height increase(s) of the first polymerlayer can be controlled by adjusting the size distribution of the blockco-polymer, for example, using the RAFT polymerization technique.

In certain embodiments, in addition to selectively tuning a sensor viaswelling, the polymeric phases of the alternating layers of polymericmaterials may be designed to affect particular wave propagation modes.For example, the polymeric materials of the polymer layers may be chosenso that, in the presence of a target analyte of interest, a periodicchange of refractive index (n₁) in the various photonic materialsoccurs. Indeed, in some applications of the present invention, the merepresence of an analyte in a cavity in the first polymer layer can leadto a change in the refractive index (n₁) of the first polymer layers.Advantageously, such a change may result in a reflection of light of aselectively different wavelength.

In particular, whereas a swelling effect can enable users to opticallytune a sensor using changes in the thickness or shape of the polymerlayers within a sensor, molecular binding or disposition of an analytein a cavity of the first polymer layer can enable users to opticallytune the sensor using molecular changes affecting, for example, theindex of refraction of the polymeric phase. More specifically, molecularbinding may change the average refractive index according to theeffective medium theory. For example, if n₁ is the refractive index ofthe polymeric material in the first polymer layers and n₀ is therefractive index of the air in the cavities in the absence of theanalytes, then the average refractive index of the first polymer layersin the absence of the analytes depends upon the values of both n₁ andn₀. Once analytes having a refractive index of n₂, are received by thecavities, the average refractive index of the first polymer layerschanges to instead depend upon the values of both n₁ and n₂. This changein the average refractive index of the first polymer layers causes achange in the color of the light reflected from the sensor.

In FIG. 2, an exemplary MIP 225 with a chromophore indicatorincorporated into a polymeric phase of a first polymer layer 101 isdepicted. As previously described, in some implementations, acavity(ies) 220 may be formed in a MIP 225, e.g., after the analytemolecule template is removed. Once a fluid containing an analyte ofinterest 300 is introduced to the first polymer layer 101 and MIP 225,the presence of and re-binding of any target analyte 300 in any of thecavities 220 of the MIP 225 may transform the first polymer layer 101into a hybrid layer 310 having, for example, modified chemico-electricproperties. This transformation may be accompanied by one or more of anincrease in volume/height of the hybrid layer 310 and/or a production ofa different composition in the hybrid layer 310, which may, for example,modify the local refractive index.

Methods of Manufacture

The colorimetric chemical sensor described herein may be manufactured ina variety of manners. For example, the periodic lamellar structure maybe formed from self-assembly, microfabrication, or other appropriatemethods. Exemplary bottom-up and top-down methods of manufacture aredescribed below.

Bottom-Up Methods of Manufacture

Referring to FIGS. 3A and 3B, an exemplary bottom-up method to produceeach polymer layer of a lamellar photonic material is shown. In someimplementations, a co-polymer may be synthesized as described herein tofacilitate the microphase separation for self-assembly. For example, asecond polymer layer 102 can include polystyrene 402, formed fromstyrene monomers 406. A first polymer layer 101 may be formed, with achromophore indicator as a co-polymer, for example,poly(urea-naphthalimide-styrene) (PUNS) polymer 404.

Referring to FIG. 4, an exemplary polymerization synthesis route to forma self-assembled photonic material is depicted. The first and secondlayers are self-assembled into a one-dimensional structure rather than athree-dimensional cube. The self-assembly is accomplished due to thehydrophilic nature of the first polymer layer and the hydrophobic natureof the second polymer layer. For example, the block co-polymer insuitable solvent (e.g., propylene glycol methyl ether acetate (PGMEA))can be spin-coated onto a suitable substrate such as glass.

In some implementations, as depicted, a block co-polymer of, e.g.,polystyrene (first polymer layer) and poly(urea-naphthalimide-styrene)(second polymer layer) may be synthesized via, e.g., reversibleaddition-fragmentation chain transfer (RAFT) polymerization. Subsequentto the formation of the block co-polymer, it can self-assemble into thephotonic material. Other polymerization methods, including but not limitto, atom-transfer radical polymerization (ATRP), may be used to controlthe molecular weight and distribution, as can RAFT polymerization.

Such a structure can also be produced by layer-by-layer assembly, forexample, via spin-coating or dip-coating of each of the respectivelayers to form the alternating first polymer and second polymer layers.For example, the first polymer layer can be made from a pre-polymerwithout styrene blocks. The second polymer layer can be liquidpolystyrene. Each of these polymers can be dissolved in appropriatesolvent (e.g., water, ethanol, and/or propylene glycol monomethyl etheracetate) in suitable concentrations. Each of the polymers in thesolvents then can be alternatingly spin-coated or dip-coated on to aselected substrate to form the final structure. Finally, the photonicmaterial or sensor can be removed from the substrate, for example, bypeeling, if the substrate is not the intended end use product. See,e.g., “Layer-by-Layer Assembly of Light-Responsive Polymeric MultilayerSystems,” ADV. FUNCT. MATER. (2014), 24: 5624-5648.

Top-Down Method of Manufacture

Referring to FIGS. 5A through 5D, an exemplary embodiment of a top-downfabrication technique for forming a lamellar, colorimetric sensor thatis capable of detecting an analyte of interest in a fluid sample isshown. In particular, FIGS. 5A through 5D illustrate a technique forforming a diffraction grating sensor of the type depicted in FIG. 1D. Insome implementations, in a first step (FIG. 5A), a first polymer layer(e.g., poly(urea-naphthalimide) MIPs, or poly(thiourea-naphthalimide)MIPs, or the like) is placed on a polydimethylsiloxane (PDMS) stamp 500,a silicon mold, or the like. In some embodiments, the first polymer is asoluble polymer (e.g., a soluble MIP polymer including a chromophore)that is dissolved in a suitable solvent and then coated on the stamp 500(or mold) via, for example, a spin coating process or a dip-coatingprocess.

In some variations, the stamp 500 (or mold) includes a plurality ofteeth 502 that are spaced 504 apart to provide a desired periodicdistribution between adjacent first polymeric phases 505 a, 505 b . . .505 n of predefined dimension, thereby creating spaced apart firstpolymer layers. As previously described, each of the first polymerlayers 505 a, 505 b . . . 505 n can include or can be a molecularlyimprinted polymer having one or more cavities that are adapted toreceive an analyte of interest.

In various embodiments, the stamp is made from a uniform mold via astandard semiconductor process so that the uniformity among and betweenthe teeth can be well controlled. For example, the stamp 500 may be madevia a dry etching process, a wet etching process, or an e-beamlithography process. Having a uniform area on each tooth of the stampand uniform spacing between each tooth allows one to place a uniformamount of the first polymer on each tooth and for the first polymerlayers to be periodically spaced, which aids in ensuring that theabove-described volume changes in each first polymer layer aresubstantially the same.

In some implementations, so that the stamp (or mold) may be more easilyreleased from the co-polymer surface after an imprinting step, a thinrelease medium/molecule layer may be coated on the stamp (or mold), forexample, on the surfaces of its teeth, prior to placing the firstpolymer on the stamp (or mold). Exemplary release media, for the purposeof illustration and not limitation, include a hydrophobic monolayermolecular coating, a fluorinated self-assembled monolayer, and afluorinated diamond-like carbon coating.

In a second step (FIG. 5B), the stamp 500 prints, imprints, transfers,or the like the first polymer layers 505 a . . . 505 n onto a secondpolymer layer 503 located on or coated on a glass surface/substrate 508.In one embodiment, the second polymer layer 503 is a UV-curable polymer,for example, a liquid polystyrene, and it is coated on the substrate 508as a uniform thin film. In a final step (FIG. 5C), the stamp 500 iswithdrawn, releasing and leaving the first polymer layers 505 a . . .505 n in the second polymer layer 503. The second polymer can be in aliquid state such as a liquid polystyrene or liquid functionalizedpolystyrene. A liquid second polymer layer can be displaced by the firstpolymer layer on the teeth of the mold. Before removal of the mold asshown in FIG. 5C, a liquid second polymer layer can be solidified, forexample, by ultraviolet (UV) curing or thermal treatment.

In certain embodiments, also prior to removal or after removal of themold, the first polymer layer can be adhered to or bonded to thesubstrate, for example, covalently bonded to the substrate via thiolterminal groups of the first polymer layer (which can be present afterthe reduction of the RAFT agent. In particular embodiments, suchattachment of bottom-up manufactured sensors can be realized to varioussubstrates.

In certain embodiments, thiol groups can be reacted with silane couplingagents such as chlorosilane so that the first and/or second polymerlayer can be covalently bonded to a glass surface. Alternatively, aglass surface may be functionalized with a silane coupling agent, forexample, 3-(trimethoxysilyl)propylmethacrylate, then a thiol-ene clickreaction can be employed to covalently bond the thiol terminal groups tothe substrate. See, e.g., “Thiol-ene ‘click’ reactions and recentapplications in polymer and materials synthesis,” POLYM. CHEM. (2010),1: 17-36; and “Thiol-ene ‘click’ reactions and recent applications inpolymer and materials synthesis: A first update,” POLYM. CHEM. (2014),5: 4820-4870.

For non-glass surfaces such as other polymers, for example, plastics,surface treatment can include using oxygen plasma to activate thesurface and generate sufficient hydroxyl (—OH) groups. A suitable silanecoupling agent (e.g., 3-(trimethoxysilyl)propylmethacrylate) can beapplied to the treated surface to produce a functionalized surface withterminal vinyl groups, which can react with thiol groups via a thiol-enereaction as described herein. Physical binding such as thermal annealingalso can be used to fuse the polymer layers to a substrate.

In particular embodiments, if a sensor is pre-formed on glass, flexibleglass or other substrate, then the glass, flexible glass or othersubstrate can be bonded or otherwise adhered to glass drinkware usingappropriate silane coupling agents, for example, as described herein.

In some embodiments, an option for adhering the polymer layers to asubstrate can include introducing amine groups to substrate via silanechemistry, for example, using (3-aminopropyl)triethoxysilane (APTES) togenerate a functionalized surface with terminal amine groups, which canact as anchors to immobilize the polymer layers.

The above-described micro-imprinting technique may produce a periodicphotonic material having alternating layers of first and second polymers(FIG. 5D), similar to the self-assembled photonic materials describedabove, after the stamp (or mold) is released.

In some implementations, both the self-assembled and fabricated photonicstructures combine the exemplary and non-limiting benefits of the colorchanges that can result from structural changes in the photonicmaterials with the color enhancing capability of the MIP chromophore,for example, upon binding with analyte target molecules.

In certain embodiments, the sensor of the invention is made separatelyfrom a manufacturing process for the drinkware (e.g., cup, glass, straw,stirrer, etc.). Once the sensor is made (e.g., using any of themanufacturing techniques described above), it can be bonded or otherwiseadhered to the drinkware through, for example, a thermal adhesionprocess, covalent bonding, or a laser fusing process.

In some embodiments, the presence of the RAFT agent at the terminal endof the polymer chains can permit bonding to the surface of the drinkwareobject.

Practice of the invention will be more fully understood from thefollowing example, which is presented herein for illustrative purposesonly, and should not be construed as limiting the invention in any way.

Example

In various embodiments, for example referring to FIG. 6, thecolorimetric sensor described herein with reference to FIGS. 1A-1C, andprepared, for example, by the reaction schemes set forth in Schemes 1and 2 or 3 described hereinabove, is disposed (e.g., as a thin film)upon or integrated within a surface of a substrate 700. In its normal orcustomary means of use, the substrate 700, the surface thereof, and thesensor disposed upon or integrated within that surface are exposed to aliquid 705 in which an analyte of interest may or may not be present.For the purpose of illustration and not limitation, exemplary substrates700 include a straw 710, a swizzle stick or stirrer 715, a fluidreceptacle 720 (e.g., a cup, a glass, and the like), and so forth.

In a first step, a fluid sample to be interrogated, e.g., a beverage, isbrought into contact with the sensor. This may occur, for example, bypouring the beverage into a fluid receptacle into which the sensor hasbeen integrated; by inserting a straw, stirrer, or swizzle stick intowhich the sensor has been integrated into the beverage; and so forth. Insome applications, visual indicia of the sensor after initial contactwith the beverage may provide a neutral or “safe” reading, e.g., thesensor may reflect blue light. If an analyte of interest is introducedinto the beverage, a color change in the sensor, e.g., from blue to red,indicates that analyte is present in the fluid sample. Thus, in a secondstep, the sensor produces a color change when it comes into contact withthe beverage. Advantageously, the sensor may be able to detect thepresence of an analyte of interest for an extended period of time, suchthat a single sensor may be used to continue to detect for hours whetheror not an analyte of interest is present in the beverage.

INCORPORATION BY REFERENCE

The entire disclosures of each of the patent documents and scientificarticles cited herein are incorporated by reference herein in theirentirety for all purposes.

EQUIVALENTS

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The foregoingembodiments are therefore to be considered in all respects illustrativerather than limiting on the invention described herein. Scope of theinvention is thus indicated by the appended claims rather than by theforegoing description, and all changes that come within the meaning andrange of equivalency of the claims are intended to be embraced therein.

What is claimed is:
 1. A colorimetric sensor for detecting an analyte ofinterest in a fluid sample, the sensor comprising: a lamellar photonicmaterial comprising alternating layers of a first polymer layer and asecond polymer layer, each first polymer layer being a molecularlyimprinted polymer defining a cavity shaped to receive an analyte ofinterest, wherein the photonic material is configured such that, when ananalyte contacts the photonic material and becomes disposed within acavity of the molecularly imprinted polymer, a refractive property ofthe photonic material changes thereby to cause a detectable color changein the sensor.
 2. The sensor of claim 1, wherein each first polymerlayer is adapted such that, when the cavity receives the analyte, thefirst polymer layer changes volume relative to a second polymer layer,thereby changing the refractive property of the photonic material. 3.The sensor of claim 1, wherein the alternating layers of the first andsecond polymer layers comprise a periodic distribution.
 4. The sensor ofclaim 3, wherein, in the absence of the analyte, the periodicdistribution is from about 1 nm to about 1000 nm, or from about 100 nmto about 950 nm, or from about 200 nm to about 900 nm, or from about 300nm to about 850 nm, or from about 400 nm to about 800 nm.
 5. The sensorof claim 4, wherein the periodic distribution in the presence of theanalyte is different from the periodic distribution in the absence ofthe analyte.
 6. The sensor of claim 1, wherein each first polymer layerfurther comprises a chromophore indicator such that, when the cavityreceives the analyte, the analyte causes an electronically induced colorchange of the chromophore indicator that amplifies the color change inthe sensor.
 7. The sensor of claim 6, wherein the chromophore indicatoris incorporated into the first polymer layer as a co-polymer.
 8. Thesensor of claim 7, wherein the chromophore indicator comprises anaphthalimide moiety.
 9. The sensor of claim 8, wherein each firstpolymer layer comprises poly(urea-naphthalimide),poly(thiourea-naphthalimide), poly(styrene-urea-naphthalimide) orpoly(styrene-thiourea-naphthalimide).
 10. The sensor of claim 1, whereineach second polymer layer comprises polystyrene.
 11. The sensor of claim1, wherein the lamellar photonic material is a photonic gel or aphotonic crystal.
 12. The sensor of claim 1, wherein the sensor isdisposed upon or integrated within a surface of a fluid receptacle or astraw.
 13. A method for detecting an analyte of interest in a fluidsample, the method comprising: (a) contacting a colorimetric sensor withthe fluid sample, the sensor comprising a lamellar photonic materialcomprising alternating layers of a first polymer layer and a secondpolymer layer, each first polymer layer being a molecularly imprintedpolymer defining a cavity shaped to receive an analyte of interest,wherein the photonic material is configured so that, when an analytecontacts the photonic material and becomes disposed within a cavity ofthe molecularly imprinted polymer, a refractive property of the photonicmaterial changes thereby to cause a detectable color change in thesensor; and (b) detecting whether a color change occurs when the sensoris contacted with the fluid sample, wherein a color change is indicativethat the analyte is present in the fluid sample.
 14. The method of claim13, wherein each first polymer layer is adapted such that, when thecavity receives the analyte, the first polymer layer changes volumerelative to a second polymer layer, thereby changing the refractiveproperty of the photonic material.
 15. The method of claim 13, whereinthe alternating layers of the first and second polymer layers comprise aperiodic distribution.
 16. The method of claim 15, wherein, in theabsence of the analyte, the periodic distribution is from about 1 nm toabout 1000 nm, or from about 100 nm to about 950 nm, or from about 200nm to about 900 nm, or from about 300 nm to about 850 nm, or from about400 nm to about 800 nm.
 17. The method of claim 16, wherein the periodicdistribution in the presence of the analyte is different from theperiodic distribution in the absence of the analyte.
 18. The method ofclaim 13, wherein each first polymer layer further comprises achromophore indicator such that, when the cavity receives the analyte,the analyte causes an electronically induced color change of thechromophore indicator that amplifies the color change in the sensor. 19.The method of claim 18, wherein the chromophore indicator isincorporated into the first polymer layer as a co-polymer.
 20. Themethod of claim 19, wherein the chromophore indicator comprises anaphthalimide moiety.
 21. The method of claim 20, wherein each firstpolymer layer comprises poly(urea-naphthalimide),poly(thiourea-naphthalimide), poly(styrene-urea-naphthalimide) orpoly(styrene-thiourea-naphthalimide).
 22. The method of claim 13,wherein each second polymer layer comprises polystyrene.
 23. The methodof claim 13, wherein the lamellar photonic material is a photonic gel ora photonic crystal.
 24. A method of manufacturing a colorimetric sensorcapable of detecting an analyte of interest in a fluid sample, themethod comprising: (a) creating a first set of spaced apart layers of afirst polymer, wherein the first polymer is a molecularly imprintedpolymer that defines a cavity shaped to receive an analyte of interest;and (b) imprinting the first set of layers into a second polymer therebyto create a photonic material comprising alternating layers of first andsecond polymers configured such that, when an analyte contacts thephotonic material and becomes disposed within a cavity of themolecularly imprinted polymer, a refractive property of the photonicmaterial changes thereby to cause a detectable color change in thesensor.
 25. The method of claim 24, wherein the second polymer isdisposed upon the surface of a substrate.
 26. The method of claim 25,wherein the substrate is a fluid receptacle or a straw.
 27. The methodof claim 26, wherein the fluid receptacle is a cup or a glass.
 28. Themethod of claim 24, wherein the imprinting of step (b) uses a stampand/or a mold.
 29. The method of claim 24, wherein the first set ofspaced apart layers is disposed upon a release medium.
 30. The method ofclaim 29, wherein the release medium comprises at least one of ahydrophobic monolayer molecular coating, a fluorinated self-assembledmonolayer, or a fluorinated diamond-like carbon coating.
 31. The methodof claim 24, wherein the first polymer comprises a chromophore indicatorsuch that, when the cavity receives the analyte of interest, the analytecauses an electronically induced color change of the chromophoreindicator that amplifies the color change in the sensor.
 32. The methodof claim 31, wherein the chromophore indicator is incorporated into thefirst polymer as a co-polymer.
 33. The method of claim 32, wherein thechromophore indicator comprises a naphthalimide moiety.
 34. The methodof claim 33, wherein the first polymer comprisespoly(urea-naphthalimide) or poly(thiourea-naphthalimide),poly(styrene-urea-naphthalimide), orpoly(styrene-thiourea-naphthalimide).
 35. The method of claim 24,wherein each second polymer comprises polystyrene.
 36. The method ofclaim 24, wherein the alternating layers of first and second polymerscomprise a periodic distribution.